Waste heat recovery devices are used for recovering energy from a waste heat flow of an internal combustion engine of a motor vehicle. Waste heat recovery devices known from the prior art typically comprise a fluid cycle, for example, a so-called Clausius-Rankine cycle in which a working fluid circulates. Mechanical energy is obtained from the heat stored in the working medium by various changes in state in the working fluid to which this is subjected when flowing through the fluid cycle.
Pumping devices are used for transporting the working fluid, which for example can be implemented in the form of a so-called stroke or axial piston pump. Such a stroke or axial piston pump follows the principle of action of a displacement pump in which the so-called displacer in the form of a piston executes a translational stroke movement within a working volume.
Against this background U.S. Pat. No. 3,412,453 A and U.S. Pat. No. 4,486,152 A each disclose a pumping device having a working chamber in which a piston is arranged adjustably. A first fluid line is used to introduce a fluid into the working chamber and is fluidically connected to the working chamber by means of a breakthrough arranged on an end face of the working chamber opposite the piston. A first valve element for closing the first fluid line with respect to the working chamber is arranged in the area of the breakthrough.
In addition, a second fluid line opens into the working chamber via which the fluid can again be discharged from the working chamber and specifically in the region of a position of the piston in which the working chamber has a minimal volume. A second valve element for closing the second fluid channel towards the working chamber is provided in the opening area of the second fluid line into the working chamber.
Cavitation effects which occur during the conveyance of the working fluid in the working volume frequently prove to be problematical in these stroke piston pumps. These typically result in a reduction in the amount of fluid conveyed by the pump within the stroke cycle. In extreme cases as a result of such cavitation, even individual components of the pumping device in contact with the working fluid such as, for example, valve elements or similar can be irreversibly damaged.
It is therefore an object of the present invention to provide an improved embodiment for a pumping device in which the said problems no longer occur or at most in severely restricted form.
The object is solved by the subject matter of the independent claim(s). Preferred embodiments are the subject matter of the dependent claims.